A bicycle was a two-wheeled (one behind the other) non-motorized vehicle operated by the user sitting on it and pedaling to propel it.
In 2373, Admiral Charlie Whatley told Captain Benjamin Sisko to spruce up the "floating bicycle wheel of his", referring to Deep Space 9, as the signing ceremony for Bajor's admission to the United Federation of Planets was going to occur on the station. (DS9: "Rapture")
In 2374, Tom Paris jokingly suggested to set up a bicycle in the mess hall, attach a generator and pedal home, when the USS Voyager was forced to go into gray mode. He then "volunteered" Harry Kim for using it. (VOY: "Demon")